Multiple input hydraulic amplifier



Feb. 7, 1961. H. STERN 2,970,575

MULTIPLE INPUT HYDRAULIC AMPLIFIER Hansjoeg Stern,

Feb. 7, 1961 H. STERN I 2,970,575

MULTIPLE INPUT HYDRAULIC AMPLIFIER Filed Dec. 50, 1954 2 Sheets-Sheet 2[f7 Ver? 'orx' Hang/oe@ S-er'n,

/S Attorney.

United States Patent 2,970,575 Y MULTIPLE INPUT HYDRAULIC AMPLIFIERFiled Dec. 30, 1954, Ser. No. 478,664

5 Claims. (Cl. 121-41) This invention relates to hydraulic amplifierdevices and systems and more particularly to hydraulic appara- .tus foramplifying forces or positional movements and having provision forcontrol operation in response to *two or more input signals.

' In hydraulic control systems, it has been common in the past to employa pilot valve which controls the flow of hydraulic liquid under pressureto a hydraulic motor -for positioning or driving apparatus to becontrolled. When hydraulic amplification of the control forces isrelquired, a so-called two-stage hydraulic servo control systemorhydraulic amplifier has been employed in which a5 pilot valve controlsthe position of -a second-stage con trol valve which in' turn controlsthe supply'of hydraulic pressure liquid to the hydraulic motor.Cri-pending patent application Serial No. 301,444, filed July 29, 1952`by Howard W. Avery for a vHydraulic Amplifier, now

Patent No. 2,709,421, issued May 31, 1955,andassigned l to the sameassignee as the present application'contains a disclosure and claimsdirected to an improved two-stage hydrauliccontrol system of this type.In these prior systems, provision has not generally been made for theintroduction of more than one control signal by a single pilot valve.However, it is frequently desired that several independent controlsignals may be introduced into the system.

Accordingly, it is one object of the present invention toY provide ahydraulic control system in which two or more independent control'signals may be introduced and in whichthe operation is carried out'inresponse Ito a combinationof these control signals. Prior hydraulic.control systems of the-type described above have gen'- erally beenVsubjectto' control by the position of a pilot piston and thuscontrollable primarily in accordance with 4a position signal and notdirectly in terms of a speed sig nal. `However, it is oftendesired thata hydraulic con- A-trol system should be controllable in response tospeed signals or other signals not primarily dependent upon a relatively`static position measurement.

' Accordingly, it is another object of this invention to lprovide ahydraulic control system which is controllable -in response to signalsotherrthan relatively static position signals.

-; Further`objects`-and advantages of this invention will abe apparentfrom the following specification and the 'accompanying drawings.

.1 In carrying out the above objects of this invention in -zonepreferred embodiment thereof, a hydraulic control walve is provided forcontrolling the operation of a hydraulicmotor. The control valveincludes a housing Flow: restricice inversely in response to a givencontrol valve piston movement. And individual separate flow restrictivedevices are connected to control the discharge of liquid from each ofthe chambers in accordance with control signals.

For a more complete understanding of the invention, reference should bemade to the following specification and Athe accompanying drawings,which are as follows:

Figure l is a schematic diagram of one preferred embodiment of theinvention which is incorporated in a steering control system for adirigible craft.

Figure 2 is a schematic diagram of a modified form of the inventionemployed in a steering system for a dirigible craft in which provisionis made for the introduction of both a manual control signal and anautomatic stabilization signal.

Figure 3 is a schematic diagram of a modified form of the inventionincorporated in a control for the motive fluid andv'speed of an engine.This specific form of the invention comprises a portion of the subjectmatter which is described and claimed in my concurrently filed copendingpatent application Serial No. 478,665, now Patent No. 2,879,467, for aVibratory Control Apparatus which is assigned to the-same assignee asthe present application, and

Figure 4 is a schematic diagram of another modified form of theinvention which is incorporated in a motive fluid control system Aforcontrolling the speed of an engine.

Referring more particularly to Figure l, there is shown a hydrauliccontrol valve 10 which is positionable in response to signals introducedby pilot valves 11, and 12 controlling the pressures within controlpressure cham',- bers 13 and 14 to thus control the movement of ahydraulic motor 15. Motor 15 is connected to position a steering controlsurface 16. The control operation is accomplished by positioning of thepilot valve 11 in response to movement of a manual control lever 17through the medium of an electrical solenoid 18 and an energizingcircuit therefor. A follow-up control signal is provided at the pilotvalve 12 by means of a mechanical linkage which connects this pilotvalve to follow changes in the position of the steering member 16'. Thecontrol valve 10 includes a housing 20 which may be integral with'thehousing 21 of the hydraulic 'motor 15. Within the housing 20 there is ahigh pres- 'sure inlet for the reception of high pressure hydraulicliquid at 22. This inlet as well as other inlets for high pressurehydraulic liquid shown in the drawings for this patent application isidentified also by the letter symbol 'P and an inwardly directed arrow.Similarly, the low pressure'return lines or conduits which are intendedAfor connection to a reservoir or sump of hydraulic liquid at lowpressure are indicated by the letter symbol S and -an outgoing arrow. Itwill be understood that a conventional reservoir and source of hydraulicpressure liquid may be employed. For purposes of simplicity and clarityin the drawings, these components are not shown.

The inlet 22 is the casing 20 forms a fluid pressure manifold whichterminates at ports 23 and 24 connecting to the bore of the controlvalve 10. From the ports l25 and 24, hydraulic pressure fluid issupplied through capillary passages indicated at 25 and 26 to therespective control pressure chambers 13 and 14. Valve 10 includes asleeve. member 27 which maybe considered as a portion of the housing 20and which defines a cylinder bore within which the control valve piston28 is reciprocably mounted. lThe capillary passages 25 and `26 areformed by cooperating portions of sleeve member 27 and end lands 29 and30 of piston 28 which are of slightly reduced `diameter with respect tothe cylinder bore diameter. The remainder of the valve 10, between theend lands 29 and 30, is in the general configuration of a conventionalthree-land control valve having outer lands 31 and 32 and a center land33. Center land 33 is connected to control the opening of a port 34which connects with a low pressure discharge manifold 3S. The valvelands 31, 32 and 33 therefore control the entrance and discharge ofhydraulic pressure uid to motor conduits 36 and 37 lto control themovement of the piston 3S of the hydraulic motor 15.

From the piston 3S there extends a connecting rod 39 which is pivotallyconnected to a crank 40 for movement of the steering control surface.16. Resulting movement of the steering control surface 16 istransmitted through a connecting rod 41, a bell crank 42, and aconnecting rod 43 to piston 44 of pilot valve 12.

The cylinder borey of the pilot valve 12 is connected to the controlpressure chamber 14 by means of a tluid passage 45, One of the valvelands of control valve `piston 44 includes a reduced diameter section at46 which forms a capillary passage within the valve bore for controllingthe discharge of hydraulic pressure liquid through .a port 47.Similarly, the bore of pilot valve 11 is connected with control pressurechamber 13 by a hydraulic uid passage 48, kand the piston 49 of pilotvalve 11 is provided with a reduced diameter portion indicated at 50forming a capillary passage for control of the discharge of hydraulicpressure fluid through a yport 51. The position of the piston 4 9 yofthe pilot valve 11 is determined by the energization of the solenoid 18.This solenoid may be energized from Va battery 52 across which there isconnected a potentiometer 53. A portion of the battery voltage appearingacross the potentiometer 53 may be selected by the control lever 17 forapplication to the solenoid 18. Solenoid 18 may preferably .beconstructed in accordance with .the teachings of Boynton et al. .Patent.2,435,817 .for an Electromagnet with Plunger which is assigned to thesame assignee as the present application.

In operation, .if the control lever 17 is moved so as to change theenergization of solenoid 18, the piston 49 of pilot valve 11 is thusshifted in position to change the length of the capillary passageprovided by the piston portion t) at port 51 and thereby change theresistance to flow offered by the capillary passage. The low ofhydraulic fluid through control pressure chamber 13 is thus altered and`the resulting unbalance of pressures in chambers 1,3 and 14 causes thecontrol valve 10 to move to one side to refestablish pressure balancebetween chambers 13l and 14.. This re-establishment is accom.- plishedby virtue of changes in resistance to liquid flow offered by thecapillary passages 25 and 26, such that the pressure drop through thepassage 25 at the new flow established by passages 25 and Sil is equalto the pressure drop through capillary passage 26 at the new ilowestablished by passage 26 in cooperation with passage 46. Movement ofthe control valve will actuate the motor 1S to shift the steering member16. As described above, movement of the member 16 will result in amovement of the piston 44 of the pilot valve 12. This movement will bein such a direction as to readjust the balance of pressures betweenchambers 13 and 14 so that vcontrol valve 10 will return .to thecentered position shown and no further movement of the motor and thesteering control surface will occur. More specifically, for instance, ifthe movement of pilot valve piston 49 is to the left to shorten thecapillary passage connecting with discharge port 51, the discharge ofhydraulic liquid from the control pressure chamber 13 will be increased`and the pressure within this chamber will therefore drop with respectto the pressure within chamber 14. The piston 28 of control valve 10will therefore move to the left. This movement will continue until thepressure in charnber 13 is equal` to that in chamber 14 by virtueoftheshortening of the length of passage 25. This motion chamber 13 and 14 ata lower level.

to the left in the diagram provides a high pressure fluid connectionthrough port 23 and conduit 36 to the left end of the hydraulicpositioning motor 15. Positioning motor piston 38 will therefore rnoveto the right to rotate the steering control surface 16 in a clockwisedirection. The clockwise movement of steering control surface 16 willresult in a movement to the right in the diagram of piston 44 of pilotvalve 12. This movement of the pilot valve piston 44 will reduce-thelength of the capillary passage at 46 connecting with the discharge port47 to increase the discharge of .hydraulic fluid from control pressure14 to `rebalance the pressures in control pressure This rebalancing willcause the return of the control valve piston 28 to the centered positionshown and no further control operation will occur. It will thus be seenthat for any position which is given to the control lever 17, the systemwill provide a corresponding new position for the steering controlsurface 16 which will be automatically held. Although a manual positioninput control is shown for this steering control surface positioningsystem, it will be obvious that the electrical energization of solenoid18 could be .obtained from automatic electrical control apparatus suchas an automatic pilot. Although pilot valves 11 and 12 have beenillustrated as employing capillary llow control elements at the reducedsections 59 and 46, it will be appreciated that more conventional valveswithout these reduced sections may be employed to vary associatedorifice openings.

It will be obvious, of` course, that the input pilot piston 49 of pilotvalve 11 may be manually positionable. This is illustrated in theembodiment of Figure 2 in which the `input control lever 17a positionsthe pilot piston 49a of the pilot valve 11a through -the medium of aconnecting rod 55. In the vmodification of the system shown .in Figure2, the right-hand. pilot valve 12a includes a piston 44a which ispositioned by asol'enoid 18a. The solenoid 18a is energized by anattitude stabilization damper which may include a conventional rate gyroand an electrical amplifier to provide attitude stabilization signalsfor the dirigible craft which is to be controlled by the system. Figure2 thus particularly illustrates how the present invention may beemployed to mix two control input signals such as the manual controlsignal fromthe lever 17a and the electrical signal from the attitude.stabilization damper 56 to obtain a positioning control system which isoperable in response to the mixture .of signal. Inthis embodiment of theinvention, a follow-up signal is obtained by a method which has beenemployed. in prior art systems, The entire casing 20 of the controlvalve, and the casing 21a of the hydraulic motor 15a which is integraltherewith are movable upon actuation of the motor 15a. The piston 38a ofthe hydraulic motor 15a includes a connecting rod S7 which is pivotallymounted to the frame of the dirigible craft to be controlled asindicated at 58. It will be seen therefore that the piston 38a remainsrelatively fixed and the casing 21a must move when the motor 15a isactivated. This motion is transmitted through the connecting .rod 39at-o the steering control surface 16a. Since the control valve housing 20is integral and movable with the housing 21a of the motor 15a and housesthe pilot valve 11a when the motor 15a causes motion of these housingsin response to an initial movement of the control lever 17a, therepositioning of the housing causes an immediate relative repositioningof the housing and the pilot piston 49a to provide the desired follow-upoperation.

In the embodiments of the invention shown in Figures 1 and 2 anddescribed immediately above, the two pilot valves controlling thedischarge of uid from the control pressure chambers 13 and 14 have beenstatically positionable to various control positions in order toaccomplish the control function. This control functionmay also beaccomplished byfcausing the control valve pistons Vtoopenintermittently, the amplitude or the frequency iifv the intermittent'opening action will "then provide an average discharge rate which willcontrol the Vfiow and the resulting pressures in the chambers 13 and 14.An example of a system employing this principle is shown in themodification of Figure 3. In this form of the invention, the pilot valvepistons 44b and 49b are respectively vibrated by separatespring-masssystems including leaf spring members 60 and 61 and the associatedmasses 62 and63. `These spring-mass systems are designed with naturalvibration frequencies respectively above and below a vibrationexcitation frequency which is to be controlled..Y In the system ofFigure 3, the apparatus of the invention is incorporated in a speedcontrol system for 'an engine 64 and the excitation frequency` of thespringmass systems including the spring members 60 and 61 `isproportional to the speed ofthe engine 64. This speed signal istransmitted through an output shaft 65 to an eccentricdevice 66'fromwhich a translational vibration 'is transmitted to a connecting rod 67and thus to the spring members 60 and 61. The connecting rod 67 may Ybe.supported as shown at 68.

In this system, the output shaft 39 of the power piston 38 is connectedtoposition a motive fluid valve 69 to control the flow of motive fluidto the engine 64 in order to maintain the engine speed which isdetermined by the natural vibration frequencies of the spring-masssystems including the spring members 60 and 61. A starting spring 70 maypreferably be provided `to bias the control valve in the direction whichwill provide for increase in-motive fiuid flow to the engine 64 when theengine speed is below the range at which the spring-mass systems areeffective. The system shown inFigure 3 .land described-'in` this "ari'd'the preceding paragraph forms a portion of the"subject"'rnatterdescribed and claimed Vin my concurrentlyfiled "arid ctr-pending patentapplication Serial No. 478,665; nov/"Ptent'N. 2,879,467, for a VibratoryControl Apparatus which is assignedto the same assignee as the'presentapplication. i It will be realized, of course, that the control devicessuch as pilot valves 11 and 12 not yonly may be operated .by eithermechanical Vor electrical signals asy illustrated in Figures l and 2, orby vibratory mechanical signals such as illustrated inFigure 3, but flowcontrol devices other than valve elements may be used on either one `orboth sides of thel control system of this invention. For instance, inthe modification of Figure 4,.V the pilot valve 12 is replaced by 'asmall low-fiow positive displacement pump 72. In this embodiment, thepump 72 Ais employed to provide a'speed sign-al to indicate the .speedof the engine64 as determined by -the rotation of Athe shaft 65. Thus,the manual control lever 17a may be positionedto shift'the" pilot valvepiston 49a to a position corresponding to a desired speed of the engine64,` The system then operates to adjust the setting of 'motive uidvalve-'69 to change the speed of the engine `V64 lto a pointat'which-the 'fluid flow provided by the pump 72 corresponds to the liowpermitted by the valve 11a and the pressures within control pressurechambers 13 and 14 -are Athereby balanced.

It will be apparent that there are many possible combinations ofseparate liow control devices which may be employed to control thepressures within the control pressure chambers 13 and 14, and themodifications of the invention shown and described above areillustrative only of a few of the possibilities. For instance, fiuidpumps such as the pump 72 in Figure 4 could be employed on both sides of-the system and the system could thus be employed to match the speeds oftwo machines. The speed of machine 64 would be altered or controlled by.the valve 69 to follow the speed of another machine which would rotatea pump similar to the pump 72 to control the pressure within controlpressure chamber 13.

A particularly notable feature of the invention is that with twoseparately operable pilot valves or other flow control signal inputdevices, the number of possible input signals isatleast doubled overthejconventional hydraulic servo system in which a single pilot valve isemployed. Thus, in a conventional piloted positioning system,4 twoinpnut signals may be employed by movements respectivelyof the pilotvalve piston and of the cylinder or cylinder sleeve within which thatpiston is supported. Although the movable cylinder sleeve structure hasnot been disclosed in this patent application, itis well known, and theprinciple of movement of the cyclinder supporting 4the pilot valve isillustrated in Figure 2 as described above. Obviously, by the employmentof sleeves, the pilot valves could both provide for the reception of twoinput signals to make a total of `four input signals which would behydraulically mixed in the control system. .This feature of theYinvention whereby a plurality of control input signals may be mixedhydraulically is particularly important and advantageous because: manycontrol systems require a multiplicity of input signals and the presentmethods of combining those signals are often yery unsatisfactory. Thepresent methods are very generally by means of lever systems, or systemsemploying differential gears or other mechanical connections for4combining position signals before introduction to the hydraulic pilotvalve. These prior systems have the basic 'disadvantage not existent inthe present invention that the mechanical connections are likely toinclude play or lost motion because of assembly requirements and becauseof mechanical wear after a period of use. Such lost mo- ,tion can bedisastrous in a positioning control system, particularly where theamplification is high, for extreme lack' of precision in the controlsystem is likely to result, ,and even more seriously, unstable operatingconditions may be encountered.

Incontrast, the present invention provides a system in which-signalsmay-be combined very precisely within the hydraulic systemI itselfandi-withoutthc necessityl lfor mechanical interconnections between the'separate sources of input signals. This lack of interconnection isValsoa very important advantage since the transmission of mechanicaldisturbances from one signal source to another, .commonly present inprior art systems, may be complctely avoided.

The following claims are intended todefine the valid scope of thisinvention over'the prior art. and to cover all changes and modificationsfalling within the true spirit and valid scope of' the invention. l A

What I claim as new `and desire to secure by Letters Patent of theUnited States is: f

l. A steering control system for a dirigible craft comprising a steeringmember to be positioned, a hydraulic -motor connected to position saidsteering member, a valve connected to control-said positioning motor,said .controlvalve comprising a housing enclosing two separate controlVpressure chambers and a piston reciprocably mounted within said housingbetween said chambers, said ,piston including reduced diameterend'portions defining capillary passages for the admission of hydraulicpressure fiuid into said chambers respectively associated therewith,said capillary passages being inversely variable in length and flowresistance upon piston movement, a first variable ow valve connected tocontrol the discharge of fluid from one of said chambers in accordancewith a control signal, a second variable fiow valve connected to controlthe discharge of fiuid from the other 'of said chambers, and amechanical linkage connection 7 ber enclosures at the v-respective -endsof 'said piston, the portion of said 'housingsupportingsaid pistoncomprising asleeve member ofalength shorter than said piston and havinga'cylinder bore therethrough, said piston including ends 'protrudingthrough the Vends of said sleeve and comprising end lands of reducedcross` section to provide circumferential capillary passages withtheinner surface'of .said sleeve, said respective capillary passagesbeing 'inversely variable in 'length vfora given piston movement, saidsleeve including inlet connections for supplying hydraulic pressure uidthrough said Acapillary passages to said chambers, andat least two 110Wcontrol 'devices separated from said Apiston -but arranged `to controlflow through said chambers, said ow control -devices being operable inresponse "tondependent control signals from ysaid engine.

3. A hydraulic 'positioningapparatus comprising a double input hydraulicamplier including a housing Aenclosing two separate control pressurechambers each arranged for continuous llow yof hydraulic pressure fluidtherethrough, a rst pilot valve arranged Yfor positioning invaccordancewith a `desiredoutputposition of the apparatus and connectedto control the liowfo'f Huid through one of Vsaid chambers, a secondpilot valve arranged for positioning in accordance with the actualoutput position of the apparatus and connected to control the ow of uid4'through the other ofsaid chambers, said -rst and second pilot valvesbeing operative in kresponse to independent signals of unlike kvkind, acontrol valve piston reciprocably 'mounted within said housing between`r'said control pressure chambers for positioning `'in 'accordance withpres- -sure differences therebetween, .said vcontrol valve pistonincluding end portions forming capillary rpassages with associatedportions of said housing, said capillary ypassages at said yrespectivechambers being inversely variable in length 'for-a given movement'fsa'idcorltro'lvalve piston, saidlrousin'g including-connections for thesupply of high -pressure hydraulic lluid through said capillary passagestosaid respective chambers, and Va hydraulic positioning motor connectedfor loperation by `said control valve.

4. A double input Ahydraulic amplifier for an engine speed controlsystem comprising a housing enclosing two control pressure chambersadapted for-.continuous ow of hydraulic pressure uid therethrough, aliquid ow control device connected -to control the IHow of vliquidthrough one of said chambers in accordance withia control signal, aliquid pump arranged to be drivenby'the engine which is to be controlledas an indication ofthe vspeed thereof vvand Yconnected to the-other ofsaid chambers 'for controlling the 'liquid ilow therethrough, a con-4'trol valve piston reciprocably mounted withintsaid housing between-said control ypressure chambers and arranged for positioning inaccordance with pressure dilferences there- "between, the respective-ends of said piston adjacent to :said chambers including membersforming capillary passages with associated portions of said housing,said passageslbcing variable in length upon -p'iston Lmovement,satl

housing lincluding hydraulic 'pressure zliquid inlet connections forsupplyof hydraulic pressure liquid ,throughasai'd capillary passages tosaid chambers, 'a vhydraulic positioning motor connected for positioningby saidcontrol valve, said motor `being adapted for-connectionto adevice for controlling the flow ofengine motivetluidifor the `control ofthespeed thereof.

5. A multiple {input fhydraulic ampliier forza hyfdraulic control systemproviding for control .operation in response to two or lmore:independent control fsignals, .comprising a housing, a reciprocablepiston mounted 5in-the housing 'and dividing it into two controlpressure chambers, 'ow receiving and discharging meanshassociated' witheachchamber and adapted for connection to asource of hydraulic liquidunder pressure, flow .restrictive lmeans associated with opposite sidesof said piston for restricting ow through each chamber, Yadditional Howrestrictive means responsive to a rstcontrol signal and acting-torestrict .ow through one of said chambers, vand 4further* additionalflow restrictive means responsive to a second .control signalindependent from land unlike said first con- -trol signal, said secondysignal acting .to `restrict `ilow through theother of said chambers,said controlpressure chambers and said flow restrictive means `being soconstructed and arranged that Lthe piston position'and operation isgoverned by the Lresultant'of the tlow restrictive 4forces lgenerated`by-.said first :and :second control signals.

Referencesfitediin the :file of this patent ED STATES YPATENTS 826,979Wilkinson 2---. M July '24, "1906 '826,980 1906 1,826,363 1931 2,177,098v11939 2,281.7 5`3 Y 1942 2,394,384 lHorstmann Feb. 5 '194'6 f 2,400,126Matthews May 14,1946 2,409,517 Schrn'it' Oct. 15, 1946 2,484,557 Ec'kmanOct. 11, 1949 2,503,397 Le Valley Apr. Y11, '1950 2,582,088 WalthersJan. 8, 1952 2,617,444 .Gardner Nov. 11,1952 2,678,177 'Chenery et alMay'll, 1954 2,709,421 Avery May 3'1, 1,9755 2,750,862 Garmanger June19, 19.56 ,2,767,689 `Moog Oct. 23,195.6 2,773,660 Rasmussen Dec. V11,1956 2,775,254 Stanbury Dec. 25, 1956 2,800,143 Keller July `23, 19572,877,968 Granan et al Mar. .17, 1959 'FOREIGN v PATENTS 423,676 GermanyJan. 8, 1926 874,370 France Aug. 5, .1942

